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Influence of intramuscular fat content on the quality of pig meat — 2. Consumer acceptability of m. longissimus lumborum
Meat Science 53 (1999) 67±72
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In¯uence of intramuscular fat content on the quality of pig meat Ð 2. Consumer acceptability of m. longissimus lumborum X. Fernandez a,*, G. Monin a, A. Talmant a, J. Mourot b, B. Lebret b a
INRA, Meat Research Centre, Theix, 63122 Saint-GeneÁs Champanelle, France b INRA, Pig Research Centre, 35590 L'Hermitage, France
Received 22 December 1998; received in revised form 5 March 1999; accepted 6 March 1999
Abstract The present study is part of a project which aimed to examine the in¯uence of intramuscular fat (IMF) content on sensory attributes and consumer acceptability of pork. Two experiments were conducted to evaluate consumer acceptability of pork chops with varying IMF level in muscle Longissimus lumborum (LL). Each experiment used 32 castrated male pigs selected after slaughter either from 125 Duroc Landrace (Experiment 1) or 102 Tia Meslan Landrace (Experiment 2) crossbred animals, and showing large variability in LL IMF content: from <1.5 to >3.5% in Experiment 1 and from 1.25 to 3.25% in Experiment 2. A group of 56 consumers evaluated various items on rib-eye (LL muscle trimmed of backfat) (Experiment 1) and on entire chops trimmed of backfat (Experiment 2). Data from Experiment 1 indicate that an increase in IMF level is associated with an increase in visual perception of fat and a corresponding decrease in the willingness to eat and purchase the meat, when expressed before tasting. The latter eect disappeared after the consumers had tasted the meat, probably due to a positive eect of increase IMF, up to 3.5%, on the perception of texture and taste. In Experiment 2, where entire chops were evaluated, the perception of visible fat was not aected by IMF level, probably due to the lack of variation in the level of intermuscular fat between the four IMF groups. The willingness to eat and purchase the meat were unaected by IMF level, whereas the perception of texture and taste was enhanced with increased IMF levels up to 3.25%. The present data suggest that the acceptability of pork may be improved by increasing IMF level but: (1) this eect disappeared for IMF levels higher than 3.5%, which are associated with a high risk of meat rejection due to visible fat and (2) the positive eect of increased IMF probably holds true as long as it is not associated with an increase in the level of intermuscular fat. # 1999 Elsevier Science Ltd. All rights reserved. Keywords: Pig meat; Intramuscular fat; Consumer acceptability
1. Introduction As discussed previously (Fernandez, Monin, Talmant, Mourot, & Lebret, 1999), results of the literature concerning the in¯uence of intramuscular fat level on the sensory attributes of pork are controversial. Part of the discrepancy could be due, at least in part, to the fact that confusion may occur between several factors likely to aect the sensory qualities of pork. Thus, a project was carried out to study the in¯uence of IMF level on the sensory quality and acceptability of pork, under controlled conditions (see Fernandez et al., 1999, for details). In the ®rst part of this project, using two different types of pigs free from the HALn and the RN* Corresponding author. Tel.:+33-04-73-62-41-68; Fax:+33-0473-62-42-68. E-mail address: [email protected] (X. Fernandez)
genes, it was found that increased IMF level had a positive in¯uence on the sensory attributes of pork (Fernandez et al., 1999). The increase in IMF level is generally considered as a means to enhance the eating quality of pork. Provided that IMF has a positive in¯uence on the sensory qualities, a fundamental question remains to be answered before any long term strategy is initiated. This question concerns the acceptability by consumers of meat with increased IMF, and thus visible fat. The study by Touraille, Monin, and Legault (1989) comparing dierent genetic types of pigs has shown that for crossbred pigs including Chinese blood, the improvement in sensory qualities attributed to increased IMF level was counterbalanced by a disadvantage in terms of consumer acceptability due to visible fat. This article reports the results from the tests of consumer acceptability of pork chops with varying IMF
0309-1740/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved. PII: S0309-1740(99)00038-8
68
X. Fernandez et al. / Meat Science 53 (1999) 67±72
levels. Results from chemical composition and sensory analysis have been presented in a previous article (Fernandez et al., 1999). 2. Materials and methods 2.1. Animals The animals used in the present work were the same as described in a previous report (Fernandez et al., 1999). Brie¯y, animals in Experiment 1 were 125 castrated male pigs from the Duroc Landrace crossbreeding. They originated from the same farm and were reared in collective pens on straw bedding, with ad libitum feeding up to a live weight of 100±110 kg. In Experiment 2, 102 castrated male pigs from the Tia Meslan Landrace crossbreeding were used. The pigs originated from the same farm and were reared in collective pens (9 pigs per pen) until slaughter at 100±110 kg live weight. All pigs were tested for the Hal and RN- genes, as described previously (Fernandez et al., 1999). 2.2. Sampling and measurements at slaughter The sampling and measurements at slaughter have already been described in a previous report (Fernandez et al., 1999). 2.3. Selection of experimental animals In each experiment, a group of 32 experimental pigs was selected in order to obtain a signi®cant variability in IMF content. Apart from IMF content, several criteria were retained for the selection of the 32 pigs among the slaughtered animals. The criteria to ful®l were the following: . non-carrier of the n allele of the HAL gene, . non-carrier of the RN- allele, on the basis of glycolytic potential (Fernandez et al., 1992), . pH40>6.1 (to exclude PSE meat), . pHu<6 (to exclude DFD meat). Each of the 32 selected animals was assigned to one of the 4 IMF classes determined on the basis of IMF variability in the corresponding population (see Fernandez et al., 1999, for details). Below, the classes will be referred to as class 1, 2, 3 and 4, corresponding to increasing IMF levels. 2.4. Tests of acceptability by consumers A random sample of 56 subjects, based on target means for sex (28 men and 28 women) and age range (<25, 25 to 45 and >45 years-old) was selected from the reference ®le
of ADIV (Association pour le DeÂveloppement des Industries de la Viande). All consumers had been already involved in surveys on pork acceptability and were regular shoppers and/or consumers of pork chops. Each consumer evaluated a sample from each IMF class and each sample was evaluated by 7 consumers. The tests were carried out under laboratory conditions at ADIV. 2.4.1. Experiment 1 Raw samples of muscle LL, trimmed of external fat, were evaluated by the consumers. The consumers were asked to express their willingness to purchase and consume the meat on a three points scale (yes, maybe, no), and to evaluate the aspect of the meat on a ®ve points scale (from 1, least desirable to 5, most desirable). The samples were then cooked on a grill (2.5 min at 180 C on each side) and presented to the corresponding consumers for evaluation of texture and taste (from 1 least desirable to 5, most desirable). In addition, the consumers were asked to express an overall rating of the samples (from 1, least favourable to 10, most favourable). 2.4.2. Experiment 2 The same procedure as in Experiment 1 was used except that consumers evaluated entire chops trimmed of external fat. Immediately before the test, three chops of each animal were used to evaluate the relative area occupied by intermuscular fat. The chop was traced, intermuscular fat was identi®ed on the trace and the corresponding relative area was determined. 2.5. Statistical analysis The in¯uence of IMF class on the distribution of consumers responses was tested using the Friedman non-parametric test. Where appropriate, the Wilcoxon non-parametric test was used for comparison of means. 3. Results 3.1. Experiment 1 As shown in Fig. 1, the evaluation of visible fat was signi®cantly aected by IMF class. For class 1, 12% of the consumers found the samples too fat, and 16% for classes 2 and 3. For class 4, however, 28% of the consumers found the meat too fat. The willingness to eat (Fig. 2A) and to purchase (Fig. 2B) the raw meat diered signi®cantly between IMF classes. Overall, there was a reduction in the percentage of positive answers when IMF level increased. For example, the positive answers in terms of willingness to eat the raw meat fell from 75% in class 1 to 53% in class 4. After the consumers had tasted the meat, this eect was no longer observed (Fig. 2). Signi®cant dierences
X. Fernandez et al. / Meat Science 53 (1999) 67±72
69
Fig.1. In¯uence of IMF class on the evaluation of visible fat in Experiments 1 and 2.
Fig. 2. In¯uence of IMF class on the willingness to eat (A) and to purchase (B) the meat in Experiment 1.
were found in the willingness to purchase the meat (Fig. 2B): indeed, samples from class 3 received more positive answers and less negative answers than the samples from classes 1 and 4. As shown by the decrease in the relative importance of the most favourable scores, an increase in IMF level was associated with a depreciation in the evaluation of the aspect of raw meat (Table 1). On the other hand,
evaluations of texture and taste were more favourable when IMF level increased up to 3.5% (Table 1). Above this value, i.e. for class 4, the percentage of most favourable scores fell to values similar to those observed in class 1. Similarly, the percentage of highest overall scores (most favourable) increased with IMF level up to 3.5% (from 31% for class 1 to 49% for class 3) and decreased in class 4.
70
X. Fernandez et al. / Meat Science 53 (1999) 67±72
Table 1 In¯uence of IMF class on consumer rating for the aspect of raw meat, texture, taste and overall score in Experiment 1a IMF Class
<1.5% 1.5±2.5% 2.5±3.5% >3.5%
Aspect of raw meat 4+5 scores (most favourable) score 3 1+2 scores (less favourable)
77b 15 8
76b,c 13 11
62c 33 5
52d 28 20
Evaluation of texture 4+5 scores (most favourable) score 3 1+2 score (less favourable)
45c,d 40 15
56b 31 13
62b,c 25 13
45d 37 18
Evaluation of taste 4+5 scores (most favourable) score 3 1+2 scores (less favourable)
50c 33 17
55c 27 18
71b 16 13
52b,c 40 8
Overall score 8±10 scores (most acceptable) 31c 4±7 scores (average acceptability) 65 1±3 scores (less acceptable) 4
40c 56 4
49b 49 2
34c 63 3
a
Data are expressed as percentage of answers. Between columns, dierent superscripts indicate signi®cant dierences (p<0.05) in the distribution of answers. b,c,d
3.2. Experiment 2 In this experiment the consumers evaluated entire chops trimmed of external fat. The relative chop area occupied by intermuscular fat did not signi®cantly dier between IMF classes: 18.7, 18.0, 16.1 and 16.8% in classes 1, 2, 3 and 4, respectively. The evaluation of fat on raw meat was not signi®cantly aected by IMF class (Fig. 1), neither were the willingness to eat (Fig. 3A) and to purchase (Fig. 3B) the raw meat. After tasting, the willingness to eat and to purchase the meat did not dier signi®cantly between the IMF classes, though more favourable answers were observed for classes 3 and 4, in particular for the willingness to eat the meat. Signi®cant dierences in the overall aspect of the raw meat were found (Table 1) but no clear relationship with IMF level could be drawn. Perceptions of texture and taste were more favourable when IMF increased up to 2.75% for texture, and to 3.25% for taste (Table 1). Samples from class 3 received the most favourable overall score, with no score corresponding to the less acceptable meat (scores 1 and 2). 4. Discussion In Experiment 1, the consumers evaluated the rib-eye (the muscle LL) trimmed of external fat. The data show a dierence in consumers responses to increased IMF level between raw and cooked meat. Before tasting (observations on raw meat), the willingness to eat and
to purchase the meat decrease with increasing IMF level. This is probably due to the negative in¯uence of visible fat, as shown by the evaluation of raw meat aspect (fat and overall aspect). After tasting, however, the negative in¯uence of increased IMF level on the willingness to eat and to purchase the meat is no more signi®cant. The samples containing between 1.5 and 3.5% IMF even show a slightly more favourable position. It is particularly interesting to compare the percentage of positive intentions to eat and purchase the meat, before and after tasting. Previous studies on the acceptability of pork loin carried out by ADIV, have shown that there is generally a decrease in the percentage of positive intentions after the consumers have tasted the meat (S. Gilbert, personal communication). This decrease is an average of ÿ17 points (percentage of positive answers after tasting the meat Ð percentage of positive answers before tasting the meat). This dierence is considered as a rejection score. In our case, and for Experiment 1, the rejection score for class 3 in terms of willingness to purchase was of ÿ6 points, whereas it was of ÿ19, ÿ17 and ÿ26 points for classes 1, 2 and 4, respectively. The lowest rejection score observed for class 3 is probably due to the favourable eect of IMF level, in the range of 2.5±3.5%, on the perception of texture and taste. It is of interest to see that consumers respond to increased IMF level in a similar way as sensory panels (see for instance Barton-Gade & Bejerholm, 1985; Bejerholm & Barton-Gade, 1986; Touraille et al., 1989 for in¯uence of IMF on sensory attributes). It is important to note, however, that IMF levels above 3.5% are associated to a high rejection score which may be due to a high level of visible fat and, more surprisingly, depreciation of texture and taste. Thus, the data from Experiment 1 would indicate that increasing IMF level in LL muscle up to ca. 3% could increase the acceptability or pork, but this would be counterbalanced by a decrease in the willingness to purchase the meat, probably due to visible fat. However, these conclusions should be reconsidered in the light of the ®ndings from Experiment 2. Indeed, in Experiment 2, where the consumers evaluated entire chops trimmed of external fat, the willingness to eat and to purchase the raw meat were unaected by IMF level. This is probably due to the fact that the consumers did not visually detect variations in IMF level. This also suggests that, when the consumers evaluate the entire chops, their perception of visible fat is mainly determined by the level of intermuscular fat. In the present work, the level of intermuscular fat did not dier between the four IMF classes. It should also be kept in mind that Experiments 1 and 2 used dierent types of pigs. The threshold level for the perception of visible intramuscular fat could, therefore, dier between the two experiments. However, as shown in a previous report (Fernandez et al., 1999) the L*
X. Fernandez et al. / Meat Science 53 (1999) 67±72
values of LL muscle were lower, indicating a darker appearance, in Experiment 2 than in Experiment 1. This would mean that the threshold for visible intramuscular fat would be lower than in Experiment 1, an assumption
71
which is not supported by the results from sensory evaluation of marbling (Fernandez et al., 1999) and consumer evaluation of fat appearance. Thus, it can be reasonably assumed that, in Experiment 2, the consumers
Fig. 3. In¯uence of IMF class on the willingness to eat (A) and to purchase (B) the meat in Experiment 2.
Table 2 In¯uence of IMF class on consumer rating for the aspect of raw meat, texture, taste and overall score in Experiment 2a IMF Class
1.25±1.75%
1.75±2.25%
2.25±2.75%
2.75±3.25%
Aspect of raw meat 4+5 scores (most favourable) score 3 1+2 scores (less favourable)
58b,c 26 16
43b 39 18
55c 39 6
46b 40 14
Evaluation of texture 4+5 scores (most favourable) score 3 1+2 score (less favourable)
52c,d 31 17
54d 30 16
68b 27 5
64b,c 29 7
Evaluation of taste 4+5 scores (most favourable) score 3 1+2 scores (less favourable)
57c 34 9
64b,c 27 9
68b 28 4
70b 23 7
Overall score 8±10 scores (most acceptable) 4±7 scores (average acceptability) 1±3 scores (less acceptable)
36c 60 4
39b,c 56 5
54b 46 0
39b,c 57 4
a
Data are expressed as percentage of answers. Between columns, dierent superscripts indicate signi®cant dierences (p<0.05) in the distribution of answers.
b,c,d
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X. Fernandez et al. / Meat Science 53 (1999) 67±72
did not detect the variations in IMF level because they based their evaluation on the level of intermuscular fat. 5. Conclusions The increase in IMF levels is generally considered, at least in France, as a means to enhance the acceptability of pork. The data from the present work, taken together with those reported in a previous paper (Fernandez et al., 1999) indicate that an increase in IMF level is associated with an improvement in the consumers perception of texture and taste. However, the following observations should be considered: . The eect of increased IMF levels on consumer acceptability is favourable only if IMF levels do not reach values above approximately 2.5±3.5%. Higher values are associated with an important risk of meat rejection by consumers. . The favourable eect of increased IMF levels probably holds true as long as it is not associated to an increase in the level of intermuscular fat.
Acknowledgements This work has been carried out thanks to the collaboration of C. Bazin (Pen ar Lan), D. Malter (SELPA) and Sylvie Gilbert (ADIV).
References Barton-Gade, P., & Bejerholm, A. C. (1985). Eating quality in pork. Pig Farming, 33, 56. Bejerholm, A. C., & Barton-Gade, P. (1986). Eect of intramuscular fat level on eating quality of pig meat. Proceed. 30th Europ. Meet. Meat Res. Workers, Bristol, pp. 389±391. Fernandez, X., Tornberg, E., Naveau, J., Talmant, A., & Monin, G. (1992). Bimodal distribution of muscle glycolytic potential in French and Swedish populations of Hampshire crossbred pigs. Journal of the Science of Food and Agriculture, 59, 307. Fernandez, X., Monin, G., Talmant, A., Mourot, J., & Lebret, B. (1999). In¯uence of intramuscular fat on the quality of pig meatÐ1. Composition of the lipidic fraction and sensory characteristics of muscle Longissimus lumborum. Meat Science, 53, 59±65. Touraille, C., Monin, G., & Legault, C. (1989). Eating quality of meat from european chinese crossbred pigs. Meat Science, 25, 177±186.
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In¯uence of intramuscular fat content on the quality of pig meat Ð 2. Consumer acceptability of m. longissimus lumborum X. Fernandez a,*, G. Monin a, A. Talmant a, J. Mourot b, B. Lebret b a
INRA, Meat Research Centre, Theix, 63122 Saint-GeneÁs Champanelle, France b INRA, Pig Research Centre, 35590 L'Hermitage, France
Received 22 December 1998; received in revised form 5 March 1999; accepted 6 March 1999
Abstract The present study is part of a project which aimed to examine the in¯uence of intramuscular fat (IMF) content on sensory attributes and consumer acceptability of pork. Two experiments were conducted to evaluate consumer acceptability of pork chops with varying IMF level in muscle Longissimus lumborum (LL). Each experiment used 32 castrated male pigs selected after slaughter either from 125 Duroc Landrace (Experiment 1) or 102 Tia Meslan Landrace (Experiment 2) crossbred animals, and showing large variability in LL IMF content: from <1.5 to >3.5% in Experiment 1 and from 1.25 to 3.25% in Experiment 2. A group of 56 consumers evaluated various items on rib-eye (LL muscle trimmed of backfat) (Experiment 1) and on entire chops trimmed of backfat (Experiment 2). Data from Experiment 1 indicate that an increase in IMF level is associated with an increase in visual perception of fat and a corresponding decrease in the willingness to eat and purchase the meat, when expressed before tasting. The latter eect disappeared after the consumers had tasted the meat, probably due to a positive eect of increase IMF, up to 3.5%, on the perception of texture and taste. In Experiment 2, where entire chops were evaluated, the perception of visible fat was not aected by IMF level, probably due to the lack of variation in the level of intermuscular fat between the four IMF groups. The willingness to eat and purchase the meat were unaected by IMF level, whereas the perception of texture and taste was enhanced with increased IMF levels up to 3.25%. The present data suggest that the acceptability of pork may be improved by increasing IMF level but: (1) this eect disappeared for IMF levels higher than 3.5%, which are associated with a high risk of meat rejection due to visible fat and (2) the positive eect of increased IMF probably holds true as long as it is not associated with an increase in the level of intermuscular fat. # 1999 Elsevier Science Ltd. All rights reserved. Keywords: Pig meat; Intramuscular fat; Consumer acceptability
1. Introduction As discussed previously (Fernandez, Monin, Talmant, Mourot, & Lebret, 1999), results of the literature concerning the in¯uence of intramuscular fat level on the sensory attributes of pork are controversial. Part of the discrepancy could be due, at least in part, to the fact that confusion may occur between several factors likely to aect the sensory qualities of pork. Thus, a project was carried out to study the in¯uence of IMF level on the sensory quality and acceptability of pork, under controlled conditions (see Fernandez et al., 1999, for details). In the ®rst part of this project, using two different types of pigs free from the HALn and the RN* Corresponding author. Tel.:+33-04-73-62-41-68; Fax:+33-0473-62-42-68. E-mail address: [email protected] (X. Fernandez)
genes, it was found that increased IMF level had a positive in¯uence on the sensory attributes of pork (Fernandez et al., 1999). The increase in IMF level is generally considered as a means to enhance the eating quality of pork. Provided that IMF has a positive in¯uence on the sensory qualities, a fundamental question remains to be answered before any long term strategy is initiated. This question concerns the acceptability by consumers of meat with increased IMF, and thus visible fat. The study by Touraille, Monin, and Legault (1989) comparing dierent genetic types of pigs has shown that for crossbred pigs including Chinese blood, the improvement in sensory qualities attributed to increased IMF level was counterbalanced by a disadvantage in terms of consumer acceptability due to visible fat. This article reports the results from the tests of consumer acceptability of pork chops with varying IMF
0309-1740/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved. PII: S0309-1740(99)00038-8
68
X. Fernandez et al. / Meat Science 53 (1999) 67±72
levels. Results from chemical composition and sensory analysis have been presented in a previous article (Fernandez et al., 1999). 2. Materials and methods 2.1. Animals The animals used in the present work were the same as described in a previous report (Fernandez et al., 1999). Brie¯y, animals in Experiment 1 were 125 castrated male pigs from the Duroc Landrace crossbreeding. They originated from the same farm and were reared in collective pens on straw bedding, with ad libitum feeding up to a live weight of 100±110 kg. In Experiment 2, 102 castrated male pigs from the Tia Meslan Landrace crossbreeding were used. The pigs originated from the same farm and were reared in collective pens (9 pigs per pen) until slaughter at 100±110 kg live weight. All pigs were tested for the Hal and RN- genes, as described previously (Fernandez et al., 1999). 2.2. Sampling and measurements at slaughter The sampling and measurements at slaughter have already been described in a previous report (Fernandez et al., 1999). 2.3. Selection of experimental animals In each experiment, a group of 32 experimental pigs was selected in order to obtain a signi®cant variability in IMF content. Apart from IMF content, several criteria were retained for the selection of the 32 pigs among the slaughtered animals. The criteria to ful®l were the following: . non-carrier of the n allele of the HAL gene, . non-carrier of the RN- allele, on the basis of glycolytic potential (Fernandez et al., 1992), . pH40>6.1 (to exclude PSE meat), . pHu<6 (to exclude DFD meat). Each of the 32 selected animals was assigned to one of the 4 IMF classes determined on the basis of IMF variability in the corresponding population (see Fernandez et al., 1999, for details). Below, the classes will be referred to as class 1, 2, 3 and 4, corresponding to increasing IMF levels. 2.4. Tests of acceptability by consumers A random sample of 56 subjects, based on target means for sex (28 men and 28 women) and age range (<25, 25 to 45 and >45 years-old) was selected from the reference ®le
of ADIV (Association pour le DeÂveloppement des Industries de la Viande). All consumers had been already involved in surveys on pork acceptability and were regular shoppers and/or consumers of pork chops. Each consumer evaluated a sample from each IMF class and each sample was evaluated by 7 consumers. The tests were carried out under laboratory conditions at ADIV. 2.4.1. Experiment 1 Raw samples of muscle LL, trimmed of external fat, were evaluated by the consumers. The consumers were asked to express their willingness to purchase and consume the meat on a three points scale (yes, maybe, no), and to evaluate the aspect of the meat on a ®ve points scale (from 1, least desirable to 5, most desirable). The samples were then cooked on a grill (2.5 min at 180 C on each side) and presented to the corresponding consumers for evaluation of texture and taste (from 1 least desirable to 5, most desirable). In addition, the consumers were asked to express an overall rating of the samples (from 1, least favourable to 10, most favourable). 2.4.2. Experiment 2 The same procedure as in Experiment 1 was used except that consumers evaluated entire chops trimmed of external fat. Immediately before the test, three chops of each animal were used to evaluate the relative area occupied by intermuscular fat. The chop was traced, intermuscular fat was identi®ed on the trace and the corresponding relative area was determined. 2.5. Statistical analysis The in¯uence of IMF class on the distribution of consumers responses was tested using the Friedman non-parametric test. Where appropriate, the Wilcoxon non-parametric test was used for comparison of means. 3. Results 3.1. Experiment 1 As shown in Fig. 1, the evaluation of visible fat was signi®cantly aected by IMF class. For class 1, 12% of the consumers found the samples too fat, and 16% for classes 2 and 3. For class 4, however, 28% of the consumers found the meat too fat. The willingness to eat (Fig. 2A) and to purchase (Fig. 2B) the raw meat diered signi®cantly between IMF classes. Overall, there was a reduction in the percentage of positive answers when IMF level increased. For example, the positive answers in terms of willingness to eat the raw meat fell from 75% in class 1 to 53% in class 4. After the consumers had tasted the meat, this eect was no longer observed (Fig. 2). Signi®cant dierences
X. Fernandez et al. / Meat Science 53 (1999) 67±72
69
Fig.1. In¯uence of IMF class on the evaluation of visible fat in Experiments 1 and 2.
Fig. 2. In¯uence of IMF class on the willingness to eat (A) and to purchase (B) the meat in Experiment 1.
were found in the willingness to purchase the meat (Fig. 2B): indeed, samples from class 3 received more positive answers and less negative answers than the samples from classes 1 and 4. As shown by the decrease in the relative importance of the most favourable scores, an increase in IMF level was associated with a depreciation in the evaluation of the aspect of raw meat (Table 1). On the other hand,
evaluations of texture and taste were more favourable when IMF level increased up to 3.5% (Table 1). Above this value, i.e. for class 4, the percentage of most favourable scores fell to values similar to those observed in class 1. Similarly, the percentage of highest overall scores (most favourable) increased with IMF level up to 3.5% (from 31% for class 1 to 49% for class 3) and decreased in class 4.
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X. Fernandez et al. / Meat Science 53 (1999) 67±72
Table 1 In¯uence of IMF class on consumer rating for the aspect of raw meat, texture, taste and overall score in Experiment 1a IMF Class
<1.5% 1.5±2.5% 2.5±3.5% >3.5%
Aspect of raw meat 4+5 scores (most favourable) score 3 1+2 scores (less favourable)
77b 15 8
76b,c 13 11
62c 33 5
52d 28 20
Evaluation of texture 4+5 scores (most favourable) score 3 1+2 score (less favourable)
45c,d 40 15
56b 31 13
62b,c 25 13
45d 37 18
Evaluation of taste 4+5 scores (most favourable) score 3 1+2 scores (less favourable)
50c 33 17
55c 27 18
71b 16 13
52b,c 40 8
Overall score 8±10 scores (most acceptable) 31c 4±7 scores (average acceptability) 65 1±3 scores (less acceptable) 4
40c 56 4
49b 49 2
34c 63 3
a
Data are expressed as percentage of answers. Between columns, dierent superscripts indicate signi®cant dierences (p<0.05) in the distribution of answers. b,c,d
3.2. Experiment 2 In this experiment the consumers evaluated entire chops trimmed of external fat. The relative chop area occupied by intermuscular fat did not signi®cantly dier between IMF classes: 18.7, 18.0, 16.1 and 16.8% in classes 1, 2, 3 and 4, respectively. The evaluation of fat on raw meat was not signi®cantly aected by IMF class (Fig. 1), neither were the willingness to eat (Fig. 3A) and to purchase (Fig. 3B) the raw meat. After tasting, the willingness to eat and to purchase the meat did not dier signi®cantly between the IMF classes, though more favourable answers were observed for classes 3 and 4, in particular for the willingness to eat the meat. Signi®cant dierences in the overall aspect of the raw meat were found (Table 1) but no clear relationship with IMF level could be drawn. Perceptions of texture and taste were more favourable when IMF increased up to 2.75% for texture, and to 3.25% for taste (Table 1). Samples from class 3 received the most favourable overall score, with no score corresponding to the less acceptable meat (scores 1 and 2). 4. Discussion In Experiment 1, the consumers evaluated the rib-eye (the muscle LL) trimmed of external fat. The data show a dierence in consumers responses to increased IMF level between raw and cooked meat. Before tasting (observations on raw meat), the willingness to eat and
to purchase the meat decrease with increasing IMF level. This is probably due to the negative in¯uence of visible fat, as shown by the evaluation of raw meat aspect (fat and overall aspect). After tasting, however, the negative in¯uence of increased IMF level on the willingness to eat and to purchase the meat is no more signi®cant. The samples containing between 1.5 and 3.5% IMF even show a slightly more favourable position. It is particularly interesting to compare the percentage of positive intentions to eat and purchase the meat, before and after tasting. Previous studies on the acceptability of pork loin carried out by ADIV, have shown that there is generally a decrease in the percentage of positive intentions after the consumers have tasted the meat (S. Gilbert, personal communication). This decrease is an average of ÿ17 points (percentage of positive answers after tasting the meat Ð percentage of positive answers before tasting the meat). This dierence is considered as a rejection score. In our case, and for Experiment 1, the rejection score for class 3 in terms of willingness to purchase was of ÿ6 points, whereas it was of ÿ19, ÿ17 and ÿ26 points for classes 1, 2 and 4, respectively. The lowest rejection score observed for class 3 is probably due to the favourable eect of IMF level, in the range of 2.5±3.5%, on the perception of texture and taste. It is of interest to see that consumers respond to increased IMF level in a similar way as sensory panels (see for instance Barton-Gade & Bejerholm, 1985; Bejerholm & Barton-Gade, 1986; Touraille et al., 1989 for in¯uence of IMF on sensory attributes). It is important to note, however, that IMF levels above 3.5% are associated to a high rejection score which may be due to a high level of visible fat and, more surprisingly, depreciation of texture and taste. Thus, the data from Experiment 1 would indicate that increasing IMF level in LL muscle up to ca. 3% could increase the acceptability or pork, but this would be counterbalanced by a decrease in the willingness to purchase the meat, probably due to visible fat. However, these conclusions should be reconsidered in the light of the ®ndings from Experiment 2. Indeed, in Experiment 2, where the consumers evaluated entire chops trimmed of external fat, the willingness to eat and to purchase the raw meat were unaected by IMF level. This is probably due to the fact that the consumers did not visually detect variations in IMF level. This also suggests that, when the consumers evaluate the entire chops, their perception of visible fat is mainly determined by the level of intermuscular fat. In the present work, the level of intermuscular fat did not dier between the four IMF classes. It should also be kept in mind that Experiments 1 and 2 used dierent types of pigs. The threshold level for the perception of visible intramuscular fat could, therefore, dier between the two experiments. However, as shown in a previous report (Fernandez et al., 1999) the L*
X. Fernandez et al. / Meat Science 53 (1999) 67±72
values of LL muscle were lower, indicating a darker appearance, in Experiment 2 than in Experiment 1. This would mean that the threshold for visible intramuscular fat would be lower than in Experiment 1, an assumption
71
which is not supported by the results from sensory evaluation of marbling (Fernandez et al., 1999) and consumer evaluation of fat appearance. Thus, it can be reasonably assumed that, in Experiment 2, the consumers
Fig. 3. In¯uence of IMF class on the willingness to eat (A) and to purchase (B) the meat in Experiment 2.
Table 2 In¯uence of IMF class on consumer rating for the aspect of raw meat, texture, taste and overall score in Experiment 2a IMF Class
1.25±1.75%
1.75±2.25%
2.25±2.75%
2.75±3.25%
Aspect of raw meat 4+5 scores (most favourable) score 3 1+2 scores (less favourable)
58b,c 26 16
43b 39 18
55c 39 6
46b 40 14
Evaluation of texture 4+5 scores (most favourable) score 3 1+2 score (less favourable)
52c,d 31 17
54d 30 16
68b 27 5
64b,c 29 7
Evaluation of taste 4+5 scores (most favourable) score 3 1+2 scores (less favourable)
57c 34 9
64b,c 27 9
68b 28 4
70b 23 7
Overall score 8±10 scores (most acceptable) 4±7 scores (average acceptability) 1±3 scores (less acceptable)
36c 60 4
39b,c 56 5
54b 46 0
39b,c 57 4
a
Data are expressed as percentage of answers. Between columns, dierent superscripts indicate signi®cant dierences (p<0.05) in the distribution of answers.
b,c,d
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X. Fernandez et al. / Meat Science 53 (1999) 67±72
did not detect the variations in IMF level because they based their evaluation on the level of intermuscular fat. 5. Conclusions The increase in IMF levels is generally considered, at least in France, as a means to enhance the acceptability of pork. The data from the present work, taken together with those reported in a previous paper (Fernandez et al., 1999) indicate that an increase in IMF level is associated with an improvement in the consumers perception of texture and taste. However, the following observations should be considered: . The eect of increased IMF levels on consumer acceptability is favourable only if IMF levels do not reach values above approximately 2.5±3.5%. Higher values are associated with an important risk of meat rejection by consumers. . The favourable eect of increased IMF levels probably holds true as long as it is not associated to an increase in the level of intermuscular fat.
Acknowledgements This work has been carried out thanks to the collaboration of C. Bazin (Pen ar Lan), D. Malter (SELPA) and Sylvie Gilbert (ADIV).
References Barton-Gade, P., & Bejerholm, A. C. (1985). Eating quality in pork. Pig Farming, 33, 56. Bejerholm, A. C., & Barton-Gade, P. (1986). Eect of intramuscular fat level on eating quality of pig meat. Proceed. 30th Europ. Meet. Meat Res. Workers, Bristol, pp. 389±391. Fernandez, X., Tornberg, E., Naveau, J., Talmant, A., & Monin, G. (1992). Bimodal distribution of muscle glycolytic potential in French and Swedish populations of Hampshire crossbred pigs. Journal of the Science of Food and Agriculture, 59, 307. Fernandez, X., Monin, G., Talmant, A., Mourot, J., & Lebret, B. (1999). In¯uence of intramuscular fat on the quality of pig meatÐ1. Composition of the lipidic fraction and sensory characteristics of muscle Longissimus lumborum. Meat Science, 53, 59±65. Touraille, C., Monin, G., & Legault, C. (1989). Eating quality of meat from european chinese crossbred pigs. Meat Science, 25, 177±186.